This invention relates to devices for analysing a tool, particularly a cutting tool for use with a machine tool. It may be used, for example, for determination of the position of the cutting tool, as in tool setting, or to determine its condition, e.g. whether it is broken or worn.
International Patent Application No. WO 2004/056528 describes such a tool setting device, using a so-called “break beam” system. A light beam passes between a light transmitter and receiver. A toothed cutting tool is rotated as it enters this beam. A complex signal from the receiver is digitised in an analogue-to-digital converter, to produce a numerical representation of the receiver signal. This is then processed digitally in a digital signal processor (DSP), or in a field-programmable gate array, an application specific integrated circuit or a general-purpose microprocessor e.g. a programmable integrated circuit (PIC) or a personal computer system, in order to detect the tool from characteristic features of the signal.
When a tool is recognised, the processor produces a trigger signal which is taken to a so-called “skip” input of the computer numerical control (CNC) of the machine tool. This causes the controller to read the instantaneous values of the position encoders of the machine tool, from which is generated an offset value for use when positioning the cutting tool for cutting operations.
Such a system gives repeatable measurement results without requiring a slow feed rate for the movement of the tool into the beam, so as to provide quick operation. It also enables the rejection of extraneous signals which are not the result of the tool breaking the beam, in particular when drips of the machine tool's coolant pass through the beam.